Functionalized Regulation of Metal Defects in ln2S3 of p-n Homojunctions.

The introduction of metal vacancies into n-type semiconductors could efficiently construct intimate contact interface p-n homojunctions to accelerate the separation of photogenerated carriers. In this work, a cationic surfactant occupancy method was developed to synthesize an indium-vacancy (VIn)-enriched p-n amorphous/crystal homojunction of indium sulfide (A/C-IS) for sodium lignosulfonate (SL) degradation. The amount of VIn in the A/C-IS could be regulated by varying the content of added cetyltrimethylammonium bromide (CTAB). Meanwhile, the steric hindrance of CTAB produced mesopores and macropores, providing transfer channels for SL. The degradation rates of A/C-IS to SL were 8.3 and 20.9 times higher than those of crystalline In2S3 and commercial photocatalyst (P25), respectively. The presence of unsaturated dangling bonds formed by VIn reduced the formation energy of superoxide radicals (•O2-). In addition, the inner electric field between the intimate contact interface p-n A/C-IS promoted the migration of electron-hole pairs. A reasonable degradation pathway of SL by A/C-IS was proposed based on the above mechanism. Moreover, the proposed method could also be applicable for the preparation of p-n homojunctions with metal vacancies from other sulfides.

Visible Light-Driven Reforming of Lignocellulose into H2 by Intrinsic Monolayer Carbon Nitride.

The photoreforming of lignocellulose is a novel method to produce clean and sustainable H2 energy. However, the catalytic systems usually show low activity under ultraviolet light; thus, this reaction is very limited at present. Visible light-responsive metal-free two-dimensional graphite-phased carbon nitride (g-C3N4) is a good candidate for photocatalytic hydrogen production, but its activity is hindered by a bulky architecture. Although reported layered g-C3N4 modified with active functional groups prepared by the chemical exfoliation enhances the photocatalytic activity, it lost the intrinsic structure and thus is not conducive to understand the structure-activity relationship. Herein, we report an intrinsic monolayer g-C3N4 (∼0.32 nm thickness) prepared by nitrogen-protected ball milling in water, which shows good performance of photoreforming lignocellulose to H2 driven by visible light. The exciton binding energy of g-C3N4 was estimated from the temperature-dependent photoluminescence spectra, which is a key factor for subsequent charge separation and energy transfer. It is found that monolayer g-C3N4 with smaller exciton binding energy increases the free exciton concentrations and promotes the separation efficiency of charge carriers, thereby effectively improving its performance of photocatalytic reforming of lignocellulose, even the virgin lignocellulose and waste lignocellulose. This result could lead to more active catalysts to photoreform the raw biomass, making it possible to provide clean energy directly from locally unused biomass.

Highly efficient charge transfer in CdS-covalent organic framework nanocomposites for stable photocatalytic hydrogen evolution under visible light.

A facile and effective impregnation combined with photo-deposition approach was adopted to deposit cadmium sulfide (CdS) nanoparticles on CTF-1, a covalent triazine-based frameworks (CTFs). In this system, CTF-1 not only acted as supporter but also served as photocatalyst and electron donor. The performance of the obtained CdS deposited CTF-1 (CdS-CTF-1) nanocomposite was evaluated by H2 evolution reaction under visible light irradiation. As a result, CdS-CTF-1 exhibited high H2 production from water, far surpassing the CdS/CTF-1 nanocomposite, in which CdS was deposited via solvothermal method. The high activity of CdS-CTF-1 was attributed to the confined CdS nanoparticles with small size, leading to expose more active sites. In addition, time-resolved spectroscopy indicated that the superior performance of CdS-CTF-1 also can be ascribed to the fast electron transfer rate and injection efficiency (KET = 0.18 × 109 s-1, ηinj = 39.38%) between CdS and CTF-1 layers, which are 3.83 times faster and 4.84 times higher than that of CdS/CTF-1 nanocomposite. This work represents the first example on using covalent organic frameworks (COFs) as a support and electron-donor for fabricating novel CdS-COF nanocomposite system and its potential application in solar energy transformations.